Kuroko-type Deposits in Sangkaropi Area, Sulawesi, Indonesia

Abstract

Several kuroko-type ore deposits occur in the central part of western Sulawesi, Indonesia. The state corporation P.T. Aneka Tambang is prospecting the Kuroko-type deposits in the Sangkaropi kuroko area where the Sangkaropi (Batu Marupa), Rumanga and Bilolo deposits are now exploring. The area is situated in the western Sulawesi arc which at that time acted as the volcanic arc.The volcanic activity seems to have been almost contemporaneous with that in the Japanese "Green Tuff" region in Miocene, where all kuroko-type deposits in Japan are distributed in a relatively narrow zone.
The formation of deposits distributed in the Sangkaropi area is closely associated with the extensive submarine volcanism. The deposits are composed of stratiform. or broken stratiform and stockwork ore bodies of kurokotype, containing no gypsum ore. It can be seen at outcrops in the Sangkaropi area that the stratiform ore bodies are covered with a thin layer of barite at the top.
Sulfide minerals constituting the ore deposits are sphalerite, galena, chalcopyrite, pyrite, tetrahedrite, bornite, chalcocite and covelline with quartz, barite and clay minerals. A colloform texture is frequently observed in the fine grained stratiform ore of the Sangkaropi deposits.
The feature of ores and mineral assemblages of ore deposits in the Sangkaropi area resemble to those of the kuroko-type ore deposits in Japan, excluding a marked distinction of the absence of gypsum ore.
The filling temperatures of fluid inclusions in sphalerite and quartz from druse and vein range from 160°to 346°C. This is almost the same as that of the kuroko-type deposits in Japan.